This invention relates to methods for selecting terminals with which telecommunication connections are established. These methods are typically employed in connection with groups of terminals, sometimes staffed with human operators, that are charged with performing certain selected tasks and which, generally are fungible. That is, it is unimportant to which of the terminals an incoming call is connected.
One such method is normally referred to as “hunting.” It refers to the notion that when there is a group of terminals, for example, telephones on a group of desks in an insurance company's office, an incoming call is connected to a switching apparatus, that steps through the group of telephones, in a predetermined sequence, starting with the first telephone in the sequence, to find the first telephone that is not busy. The incoming call is then connected to that telephone. When a non-busy telephone is not found when the switching apparatus reaches the end of the sequence, the incoming caller is sent a “busy” signal. This method is sometimes called linear hunting.
Another method, which is closely related, is sometimes called circular hunting. In circular hunting the switching apparatus also steps sequentially through the sequence of telephones in the group, but rather than start with the first telephone in the sequence, the switching apparatus starts with the line succeeding the last telephone that was connected. When the switching apparatus reaches the end of the sequence without finding a non-busy telephone, the hunting for a non-busy telephone continues from the beginning of the sequence. A “busy” signal is sent to the incoming call only when the switching apparatus hunting returns to the telephone from whence the hunting began. One can think of it as hunting in modulus arithmetic, with the modulus being the number of telephones in the group.
It is quite clear that linear hunting burdens the telephones at the beginning of the sequence more than the telephones at the end of the sequence. Circular hunting distributes the burden more evenly. However, circular hunting does not take into account the idle times of telephones and, therefore, even circular hunting has the potential for utilizing the telephones in the group in an uneven manner. When human operators staff the telephones, every effort needs to be made to utilize all of the telephones in the group as evenly as possible, because one want to burden the operators who use the phones fairly.
Still another method that is employed for allocating communication, which takes into account idle times is called automatic call distribution. Switching apparatus that performs the automatic call distribution is normally call an automatic call distributor, or ACD. The ACD keeps track of the busy/idle state of the telephones in the group, and the durations of the idle time. When a call comes in, it is routed to the idle telephone with the longest idle time. If none are idle, then a “busy” signal may be returned or, in some systems, the caller may be placed in a queue.
In each one of the above-described methods, the switching apparatus knows the busy/idle state of the telephones in the group, knows the number of telephones in the group, and all of the telephones in the group are actually connected to the switching apparatus.
It is desirable to have similar capabilities in a distributed environment, where there is no switch that knows the status of any of the elements in the hunt group, ACD, or circular hunt group. Packet switching systems, for example, often don't have state information about the network's end points (terminals) that are connected to the various switches, and/or routers, in the packet switched network.